This invention relates in general to drainage of fluid from within the human body and, in particular, to a catheter system to drain fluid from cavities of the body.
More specifically, but without restriction to the particular use which is shown and described, this invention relates to an improved shunt system by which fluid may be effectively drained to reduce fluid pressure and fluid volume in a body cavity, such as in the ventricles of the brain.
Typically, numerous types of catheter systems are employed to drain fluid which accummulates in various regions of the human body. A particularly well known use of such a catheter system is found in the treatment of a condition known as hydrocephalus. The term hydrocephalus generally refers to a physiological entity in which fluid tends to accummulate within one or more compartments of the brain. The presence of such excess fluid and pressure within the brain area of a human can lead to serious medical problems for the individual, if the symptoms of hydrocephalus are not treated. Generally, various techniques have been relied upon to relieve the presence of excess fluid and pressure build-up within the central nervous system as occurs in this disease. The use of the catheter drainage systems has in the past been helpful in this treatment, and is well founded.
The first recorded attempt at mechanically shunting hydrocephalus is generally considered to have occurred in 1898. Since that time, many different methods of allievating the symptoms of hydrocephalus have been attempted. It was not until the early 1950's that mechanical shunts achieved any significant degree of success in controlling hydrocephalus. In its simpliest form, a shunt is merely a fluid control system having a proximal catheter inserted into a lateral ventricle of the brain, or such area where fluid build-up occurs, and a shunt or conduit system extending downward from that area into a lower region of the body for disposition of CSF. Generally, a shunt system terminates at a distal end at a point where the body may readily dispose of the fluid that is drained through the system, such as, within the abdominal cavity or into a vein of the heart in some cases.
Many variations of the basic shunt design have been attempted in order to improve the hydrodynamics and reliability of shunts. Nevertheless, known shunt systems continue to be subjected to numerous deficiencies in performance and reliability which arise during their use in the human body. For example, with the implantation of any shunt system, be it ventricular-peritoneal, ventricular-artrial, or the like, the device must have the capability to accommodate growth in patients who have not reached adulthood. A current practice is to pass an additional amount of catheter into the distal receptor site so that, at least theoretically, the shunt can "grow" with the patient and not require replacement or modification due to insufficient length. It has also been attempted in the prior art to provide a system having a packet of coiled distal catheter inside the chest so that it might uncoil as the patient grows. Another attempt at achieving growth capability in a shunt system is disclosed in U.S. Pat. No. 3,623,484 to Schulte. The system shown in the Schulte patent, however, has not proved clinically successful, since it only provides an elongation of two inches in a patient and has not provided practical.
In another problem posed by known shunt systems, the sedimentation of protein and debris in cerebrospinal fluid tends to plug the valve at the distal or proximal end of the shunt system. For example, such an accumulation of sedimentation occurs in one particular known shunt system, because there exists a dead space of approximately two millimeters between the distal end valve slits and the distal end plug or between the proximal end and the fenestrations. It is within this dead space that debris builds up to the point where it interferes with proper shunt operation and hence, prevents suitable drainage of fluid from the ventricle. This is known as a malfunction.
Ever since the first practical shunts were placed in the lateral ventricle, the problem of encroachment by body tissues into the inlet fenestrations has been recognized. This tissue invasion, most notably by the choroid plexus, is one of the major causes of proximal end related malfunctions. Many techniques have been employed to physically separate the catheter from the choroid plexus and/or ependymal lining. Such restraining systems are disclosed in U.S. Pat. No. 3,419,010 to Williamson; U.S. Pat. No. 3,516,410 to Hakim; U.S. Pat. No. 3,626,950 to Schulte; and U.S. Pat. No. 3,669,116 to Heyer. Unfortunately, none of the foregoing techniques of maintaining the catheter in spaced relationship to the walls have been successful, and encroachment by body tissue inherently occurs.
The regulation of intercranial pressure in the shunting of fluid in hydrocephalic patients has also presented difficulties in the use of prior catheter systems. In the prior art, regulation of pressure is accomplished typically by two distinct techniques. A common device for pressure regulation involves a valve placed in the shunt line at a level slightly below the occipital horn of the lateral ventricle. The other common type of system utilizes a valving mechanism situated at the outlet of the catheter at its distal end, such as within the abdomen. The actual construction of such regulatory valves previously employed has varied enormously from system to system. However, the slit-type valve is generally a commonly used form in popular shunts, such as in a typical one piece system. The slit valve is a simple device positioned at the distal end, in which the edges of the slit expand apart when internal pressure exceeds a predetermined value, to allow the buildup of fluid within the ventricle to pass until the pressure decreases, and the edges once again approximate. An advantage of this type of valve is that it acts as a one way valve, and a greater pressure on the outside only serves to close the valve. One example of a typical slit valve disposed at the distal end is disclosed in U.S. Pat. No. 3,111,125 to Schulte. However, there are advantages for valve usage at the proximal end to control pressure. At the proximal end, no stagnant reservoir or column of cerebrospintal fluid is created which could include sediment and cause valve malfunction.
The management of hydrocephalus is also at times complicated by patients having large ventricles. When such large ventricles are shunted, a risk of collapsed ventricles is present, because of the decreased pressure that can ultimately result in subdural fluid collections, due to tearing of the cortical mantle away from its covering. This consideration often greatly complicates the overall effective management of the patient having hydrocephalus. Experimental studies have shown that a simple shunt is not perfectly addressed to the hydrodynamic needs of the patient with severe hydrocephalus. Animal studies have shown that to obtain proper rebounce of cerebral mantle thickness, a lower interventricular pressure must be established to allow for the rebounce followed by a subsequent slight increase within the normal pressure range.
In the patient with either an unusually high pressure or large ventricles and a closed intercranial space, the advantage of a variable pressure valve becomes important. Modifications to shunts so that flow can be terminated have been made previously in attempts to lessen the rapid decompression of the interventricular space when desired. However, the deficiencies of such prior "on-off" shunts are well known in the art.
Other shortcomings are associated with the use of conventional treatments of hydrocephalus. In the surgical treatment of a patient with this disease, the insertion of a ventricular catheter through the cerebral mantle and into the ventricle requires a rigid support guide, because the catheter itself is too flexible. Various shunt systems known in the prior art employ different methods to pass the catheter. One of the more prevalent techniques is to pass a trocar into the ventricle, remove the center, and then pass the proximal catheter down the trocar housing. A disadvantage of this type of trocar is its large diameter and thusly, unnecessary impact to the brain tissue as it is passed through the cortex.
In still another problem presented by known shunt systems, the complication of a column of liquid existing between the inlet and the outlet of the catheter poses a potential problem associated with the siphon effect as the patient changes position in normal activity. Prior attempts to resolve this problem have not been satisfactory in allieviating this difficulty.
Known shunt systems demonstrate other inadequacies while treating hydrocephalus. The valve located in the distal end of the popular shunt system, in the form of a single piece unit, includes several slits which are displaced outward when the pressure within the shunt reaches a given level as previously discussed. At the present time, slit type valve shunts are generally provided in three pressure ranges, high, medium and low. In most cases, the major difference in these shunts is simply the length of the slit valve, i.e., the longer the slit, the lower the resultant opening pressure will be. However, none of the slit valves heretofore allow ready adjustment to modify the pressure ranges at the time of insertion or post-insertion.
The attachment of shunt tubing to appropriate parts of the body has presented many problems. For example, the clips employed to secure the shunts in place in the past have been bulky and inconvenient to secure at surgery. In addition, prior clips have not provided access to the interior of the shunt system as needed during use.
As has been discussed, known techniques of shunting the cerebrospinal fluid from a cavity, such as the ventricle, are associated with numerous deficiencies which interfere with the effectiveness of treatment of a patient which requires the reduction of pressure and volume of fluid from a region of the body.